The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Modern motor vehicle transmissions utilize a several quart or liter fill of transmission fluid (hydraulic oil). The transmission fluid serves several purposes. First and most obvious is the lubrication of the numerous rotating and moving parts within the transmission. Second is the transfer of heat in or out of the transmission to maintain an appropriate operating temperature and third is use in the pressurized hydraulic control system of the transmission.
To achieve proper heat transfer to the ambient for cooling, a transmission oil cooler remote from the transmission may be provided with a flow of transmission fluid.
During cold weather starts, the viscosity of the cold transmission fluid can cause significant parasitic frictional losses. Depending upon the temperature, it can be several minutes before the transmission fluid temperature rises into a range where frictional losses become negligible. This delay is primarily due to the fact that only frictional heating from the rotation of parts heats the transmission fluid. During this time, fuel economy can be significantly degraded.
It is therefore apparent that improved control of automatic transmission fluid temperature is desirable.